[jawats]

All,

I have three zooms I tested today - the Adaptall-2 60-300, the Sigma 70-300 DC OS, and the Pentax DA-L 55-300 (not the PLM). Here are the results of a "quick and dirty" test I did. I think I have to be more scientific to really test these, so I am working on a method for that now. Suggestions welcome!

A Tale of Three Zooms ? Dark Conservative ? Medium

[UncleVanya]

Clearly the 300mm of the Pentax is providing more magnification than the other two. The Sigma seems to be the smallest magnification of the three. I would suggest normalizing the image size to the weakest magnification for some shots and then shoot some as you did but crop them into the same size.

[clickclick]

Looking at your next to last row of shots at the roof shingles in the background (through the trees), the Pentax lens seems to show the shingles more in focus than the sign - detail is pretty good, so I'm wondering about the focus point on the Pentax lens, and perhaps a case of front/back focus. Did you use live view for focusing and magnification and nail it on the sign directly?

[jawats]

Looking at your next to last row of shots at the roof shingles in the background (through the trees), the Pentax lens seems to show the shingles more in focus than the sign - detail is pretty good, so I'm wondering about the focus point on the Pentax lens, and perhaps a case of front/back focus. Did you use live view for focusing and magnification and nail it on the sign directly?

I did not use live view. I should do that, however. Perhaps a follow-up with live view. Also, for those of you who like the Tamron 60-300, do you often have CA issues?

[swanlefitte]

A great test is not easy. I personally think it needs multiple steps.
Can they do a good job in optimal situations, what do they excel at and where do they fail. Ouch that is a big job. Best to pick one criterion, repeat.

[clickclick]

I did not use live view. I should do that, however. Perhaps a follow-up with live view. Also, for those of you who like the Tamron 60-300, do you often have CA issues?

I like playing with lenses and doing comparisons too, but it's not easy to dial in all the pieces to do a really bullet proof test. I'll be honest, I'm not looking for your exif, so bare with me if I'm saying things you already know or did, but these are things I picked up along the way. Due to lens front/back focus issues, always use live view and then use the magnification feature to zoom in on the area so you can really tell you got it. And you may very well find manual focus will be your friend here. Tripod obviously, and make sure that shake reduction is off and remote control shutter release with a delay. And foliage can be a real bear - stuff moves too much even with a light breeze, and motion blur may distort perceptions of sharpness. Good light and low ISO, of course, and be aware some cameras may or may not have shutter shock vibrations that typically occur in lower shutter speed ranges, e.g. 1/25- 1/200th. If you dig around, you will find quite a bit of discussion on that. Simple answer seems to be the occurrence is as much sample variations as not, for example, my K-1 II doesn't seem to have it, but others do seem to have it. And I'm always amazed at how much a lens's performance changes at different apertures. There is almost always a sharpness sweet spot. Bottom line is keep at it and have fun.